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Natural Disasters

Natural Disasters. Volcanoes: Types and Eruption Styles. Magma Review. Basalt. Andesite. Rhyolite. Types of Volcanoes. Basaltic Volcanoes Shield volcanoes Cinder cones Andesitic Volcanoes stratovolcanoes Rhyolitic Volcanoes Lava domes calderas. Basaltic Volcanoes. Shield Volcanoes

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Natural Disasters

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  1. Natural Disasters Volcanoes: Types and Eruption Styles

  2. Magma Review Basalt Andesite Rhyolite

  3. Types of Volcanoes Basaltic Volcanoes Shield volcanoes Cinder cones Andesitic Volcanoes stratovolcanoes Rhyolitic Volcanoes Lava domes calderas

  4. Basaltic Volcanoes Shield Volcanoes • Large, broad gentle slopes – resembles a “warrior’s shield” • Fluid basalt able to travel great distance • Low volatile (gas) content – generally non-explosive

  5. Shield Examples Hawaiian Islands • “Big Island” – Mauna Loa, Kilauea, and Mauna Kea Mauna Loa (largest volcano)

  6. Basaltic volcanoes Cinder Cones • Small size, steep slope • Erupt when magma encounters groundwater • Single eruptive period (months to few years) • Built up by loose cinders around small crater

  7. Cinder Cone Examples Cima Volcanic Field Red Hill Amboy Crater California Cinder Cones

  8. Andesitic Volcanoes Stratovolcanoes • Alternating layers of lava, debris, and ash • Moderate volume and size • Moderate to high volatile content • Violently explosive • Erupts repeatedly

  9. Stratovolcano Examples Cascade Ranges Mt. Hood Mt. Rainier Mt. Lassen

  10. Rhyolitic Volcanoes Lava Domes • Rough dome with many spines • Very high viscosity – magma does not travel far • Low volatile (gas) content

  11. Lava Domes Examples Central California Mono Craters Wilson Butte Panum Crater

  12. Rhyolitic Volcanoes Giant Continental Calderas • Circular, enclosed depressions • Typically filled with water to form lakes • Result from collapse volcanic structure • Due to underlying emptying of magma

  13. Continental Caldera Example Yellowstone National Park Crater Lake, Oregon

  14. Explosive Eruption Styles Hawaiian Phreatomagmatic Strombolian Vulcanian Pelean Plinian

  15. Hawaiian • Low-viscosity, fluid basalt • Non-explosive

  16. Phreatic & Phreatomagmatic • Hot magma comes in contact with shallow groundwater • Water heats up and erupts steam, rock fragments, and magma • Violently explosive • Phreatic = no new magma on surface

  17. Strombolian • Distinct blasts of magma • Produce incandescent bombs • Small tephra cone results • Mildly explosive

  18. Vulcanian • Sustained eruption of rock or viscous magma to several km • Collapse to produce pyroclastic flow • Widespread tephra fall • Very explosive

  19. Pelean • Collapse of lava dome • Produce glowing avalanches (nuée ardentes) • Violently explosive

  20. Plinian • Sustained eruption columns up to 45 km • Produce widespread ash deposits • Collapse of column to pyroclastic flow • Violently explosive

  21. Eruption Warning: Volcanic Precursors • Active Volcano • Has shown activity in recorded history • Extinct Volcano • Has not shown any historic activity • Dormant Volcano • Has not shown activity in recorded history but shows evidence of activity in geologic past

  22. Long-Term Forecasting • Ancient studies help scientist assess hazards and risk posed by future volcanoes

  23. Short-Term Forecasting • Seismic waves • Magnetic field changes • Electrical Resistivity • Ground Deformation • Changes in groundwater • heat flow • Gas composition

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